Bioactivity analysis of pentacyclic triterpenoids isolated from Metrosideros polymorpha

Eleven compounds were isolated and identified from M. polymorpha , included one previously undescribed compound ( 1 ) and ten known compounds ( 2-11 ). Through NMR, HRESI-MS and ECD spectrum analysis, the planar and absolute structures of compound 1 were determined and identified as pentacyclic triterpenoid derivative. Among the rest 10 known compounds, 2-8 also were identified as pentacyclic triterpenoids. The antifungal, insecticidal activity and Glutamate dehydrogenase (GDH) inhibitory activity of the 11 compounds isolated from M. polymorpha were evaluated, and arjunolic acid ( 7 ) showed significant antifungal activity against hizoctonia solani and Magnaporthe oryzae with IC 50 values 44.20 and 38.58 mu g mL -1 , respectively. Moreover, compound 7 displayed insecticidal activity against whitefly at a 100 mu g mL -1 concentration with corrected mortality of 35.4%. In addition, compounds 2, 3, 4, 7 and 8 exhibited strong GDH inhibitory effects at both 20 and 50 mu M, and compound 4 showed the most effective activity. The underlying inhibitory mechanism of compound 4 against GDH was confirmed as competitive inhibitors through molecular docking and enzyme kinetics. These results may lead to a potential application on agricultural and clinical use.

Automated summary

Eleven compounds were isolated from M. polymorpha, including a previously undescribed compound and ten known compounds. The structures of compound 1 were determined and identified as pentacyclic triterpenoid derivative. Compound 7 showed significant antifungal and insecticidal activity.